ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 



21 



Dr. Lawson in discussing the movements that have taken place during late 

 Tertiary and Pleistocene times in the vicinity of San Pedro, says :' "It follows that, 

 while there is a very profound physical break between the Miocene and Pliocene, 

 the marine Pliocene and Pleistocene formations are intimately associated, with no 

 epoch of subaerial denudation between them." The observations of the writer also 

 show this to be true, although in some places there is evidence of local denudation 

 between the Pliocene and Pleistocene. At Deadmau Island, in particular, there is 

 evidence of a period of denudation between the two. 



Beds of a line gray sand, with gentle north dip, rest upon the Pliocene ex- 

 posed along the railroad grade leading up to the cut in the bluff in the southeastern 

 portion of San Pedro. (See diagram D, PI. XXII.) The exact relation between 

 these gray sands and the underlying Pliocene is uncertain, as detritus covers the con- 

 tact along the face of the bluff. But the gray sand beds seem to rest almost conform- 

 ably on the yellow Pliocene deposits, both having a low dip toward the north. One 

 of the layers of gray sand near the top of the bluff north of the railroad grade con- 

 tains a fauna similar to that of the lower San Pedro stratum of Deadman Island. 

 This stratum is exposed in the bluff to the north of the San Pedro valley, and also in 

 two small cuts in the bluff west of the business portion of the town. These gray 

 sand strata were continuous at one time, the San Pedro valley, which cuts them, 

 having been formed by recent erosion. 



In the bluff" to the north of the valley the fossiliferous lower San Pedro stratum 

 is about forty feet above tide level and dips northward, disappearing under detritus 

 at the mouth of a small ravine about three hundred yards from the southern end of 

 the bluff, but appearing again north of the ravine at the base of the bluff. Under- 

 lying this lower San Pedro bed are gray sandy strata which correspond to the lower 

 part of this same formation soutli of the valley, and which are unfossiliferous, except 

 in a few places. The following fossils have been found in the lower San Pedro beds 

 in the San Pedro bluffs. 



List of Fossils of the Lower San Pedro Beds at the San Pedro Bluffs. 



Angulus bultoni 

 Anomia lampe 

 Cardium corbis 

 Corhula luteola 

 Cryptomya cali/ornica 

 C'umingia californica 

 Donax cali/ornica 

 Donax lavigata 

 Hinniies giganttiis 

 Kellia laperousii 

 Kellia suborbicularis 

 Lcevicardium subulrialum 

 Lazaria subquadrala 



PELECYPODA. 



Leda var. pracitrsor 

 Leda taphria 

 Lucina acutilincala 

 Lucina californica 

 Lucina nuitalli 

 Lyonsia cali/ornica 

 Macoma nasuta 

 Macoma secla 

 Macoma yohli/ormis 

 Maclra /alcala 

 Mytilimtria nuitalli 

 Nucula castrensis 



Nucula supranlriata 

 Oslrea lurida 

 Pecten latiauritus 

 Pecten var. monotimeris 

 Paephis nalmonea 

 Psiphia iantilla 

 Scmele decisa 

 Siliijua lucida 

 Solen rosaceus 

 Solen sicarius 

 Tapes Dlaminea 

 Tcllina bodegensis 



I Post-Pliocene DIaatropbism of the Coast of Southern California. By A. C. Lawsoo. Bull. Dept. Geol., Uolv. of CaUfornia 

 Vol. 1, 1893, p. 128. 



